NTSB report on 787 coming Thursday

The National Transportation Safety Board (NTSB) will issue an interim report Thursday on the lithium ion battery fire in January aboard a parked Boeing 787 Dreamliner at Logan Airport in Boston.

A month ago, in its last briefing, the NTSB said investigators had determined that the fire on the Japan Airlines jet started with a short circuit inside a single cell of the eight-cell battery, located in an electronics bay just behind the wing.

The NTSB has been trying to establish what caused the short circuit, but experts have expressed doubt whether that will ever be known for sure, given the level of damage to the battery.

There’s no indication that the interim report will provide an answer, though it may make clearer whether or not a definitive cause is likely to be identified later.

The report is “factual in nature and does not provide any analysis,” the NTSB said in a statement Wednesday.

Boeing’s 787s have been grounded since Jan. 16, when a second battery overheated and smoldered during an All Nippon Airways flight in Japan a week after the incident at Logan.

Boeing has proposed a fix for the battery problem — which, in the absence of a known root cause, attempts to address all possible battery system malfunctions. The company is awaiting approval from the Federal Aviation Authority (FAA) to implement that fix.

The FAA is expected to give its initial response late this week or early next.